Hydraulic jack apparatus



April 6, 1965 J. P. GLASS HYDRAULIC JACK APPARATUS 4 Sheets-Sheet 1 Filed March 5, 1962 INVENTOR- JOHN P. GLASS I wi 4505? ATTQRNEY April 6, 1965 J. P. GLASS 3,176,951

HYDRAULIC JACK APPARATUS Filed March 5, 1962 4 Sheets-Sheet 3 INVENTOR. JOHN R GLASS ATTOR NiY April 6, 1965 J. P. GLASS 3,176,961

HYDRAULIC JACK APPARATUS Filed March 5, 1962 4 Sheets-Sheet 4 w JJ-IO7 F I G. I0

INVENTOR. JOHN P GLASS ATTORNEY United States Patent 3,176,961 HYDRAULIC JACK APPARATUS John P. Glass, '7 18 Lorraine Ave., Ardrnore, Pa. Filed Mar. 5, 1962, Ser. No. 177,442

3 Claims. (Cl. 254-29) This invention relates to apparatus for tensioning the wires used in pre-stressed concrete, and more particularly concerns a hydraulic jack which is used to apply tension stress to stretch metal rods, wires, and the like.

In the manufacture of pre-stressed concrete panels, steel wires or rods are stretched and anchored in a form. Then the concrete is poured into the form and cured, the anchors and form are removed, and the wires tend to contract from their previously stretched condition to thereby hold the concrete in compression. The present invention is particularly adaptable for applying tension stress to stretch the steel wires used in 'pre-stressed concrete construction, and for anchoring said wires.

Hydraulic jacks have heretofore been employed to stretch the wires in pre-stressed concrete. However, such jacks were disadvantageous because of their large size and great weight which necessitated that they be utilized in a permanent installation, and in many cases required that they be mounted on carriages and handled by more than one man.

Moreover, the distance the wire stretched under tension had to be continuously checked and correlated with hydraulic fluid pressure to obtain the desired tension stress.

Further, during the operation of previous jacks, the jack cylinder retracted and moved away from the concrete form. This required close attention on the part of the operator to insure that there would be enough clearance for the jack cylinder to retract, and to make sure that no one was in the path of the jack cylinder as it moved rearwardly.

Accordingly, it is an object of this invention to overcome the aforementioned disadvantages of the prior art.

It is another object of'this invention to provide new and improved hydraulic jack apparatus for tensioning the wires used to pre-stress concrete and the like.

It is another object of this invention to provide a hydraulic jack that is of light and compact construction, and is adapted to utilize readily obtainable commercial anchors or chucks for the gripping means.

It is another object to provide a hydraulic jack wherein the gripping means is easily and economically replaceable.

It is another object of this invention to provide a hydraulic jack which is light in weight and may be easily held and controlled by a single operator.

It is another object to provide a hydraulic jack which does not have any exposed moving parts, and which has the wire and for removing the gripping means from the wire, and having high pressure means for tensioning the wire. i

It is another object to provide a hydraulic jack having control means whereby the hydraulic pressure values are pre-set at the hydraulic pressure source, and whereby the "ice hydraulic valves may be left open and the application of tension to the wire is stopped automatically when the desired tension is reached.

Other objects and advantages of this invention, including its simplicity and economy, as Well as the ease with which it may be adapted to existing equipment, will further become apparent hereinafter and in the drawings, in which:

FIG. 1 is a view in perspective of apparatus for tensioning the wires used to pro-stress concrete and the like, including hydraulic jack, pump, and hydraulic liquid reservoir;

FIG. 2 is a view in longitudinal section of the hydraulic jack constructed in accordance with this invention, and shows the jack with low pressure being applied to the front portion of its hydraulic pressure chamber;

FiG. 3 is a view partly in section taken as indicated by the lines and arrows 3-3 which appear in FIG. 2;

FIG. 4 is a top plan view of the handle of the jack and shows the location of its ducts and valves;

FIG. 5 is a partial view in longitudinal section of the hydraulic jack of FIG. 2 on an enlarged scale and shows the position of the elements as the wire is being released from the gripping chucks.

FIG. 6 is a diagrammatic view which illustrates the flow of hydraulic fluid at low pressure being used to operate the hydraulic jack to take out the slack in the wire;

FIG. 7 is a diagrammatic view illustrating the flow of the hydraulic liquid under low pressure being used to release the gripping chuck from the wire;

FIG. 8 is a diagrammatic view showing the flow of hydraulic fluid being used to move the elements of the hydraulic jack as it tensions the wire;

FIG. 9 is a view in perspective of a modified form of the invention which utilizes electric switch and solenoid valve means as the control means for applying hydraulic pressure; and

FIG, 10 is a diagrammatic view illustrating the electrio and hydraulic circuit of the apparatus shown in FIG. 9.

Although specific terms are used in the following description for clarity, these terms are intended to refer only to the structures shown in the drawings and are not intended to define or limit the scope of the invention.

Turning now to the specific embodiments of the invention selected for illustration in the drawings, there is shown a concrete form that includes a bed 21 (which is capable of withstanding the compressive forces applied thereto by the reinforcing rods or wires), and abutment walls 22 against which anchors or chucks 23 abut when holding a reinforcing wire or rod 24 stretched to a tcnsioned condition.

The apparatus for tensioning the wire 24 includes a hydraulic jack 25 which is connected to hydraulic fluid pressure supply unit 26 by high pressure line 27, low pressure line 28, and exhaust line 29;. Unit 26 includes a motor 32, a pump 33, a fluid reservoir 34, and reducing valves 35. Valves 35 are adjustable to give any desired high and low pressure and to maintain those pressures Without fluctuation.

Hydraulic jack 25, referring now more particularly to FIG. 2, includes a housing 36 containing a hydraulic pressure chamber 37, a compression tube 38 extending forwardly from housing 36 and having a front end adapted to abut anchor 23 (which is used to hold reinforcing wire Patented Apr, 6, 1965 .3 24), a piston 41 positioned in chamber 37, a hollow tensioning rod 42 connected to piston 41 and extending forwardly from chamber 37 and positioned within compression tube 38, and a gripping chuck 43 mounted on the front end of rod 42 and adapted to grip Wire 24 when it is being subjected to tension stress.

Housing 3d includes a jack cylinder 44 which is screwed into front end cap 45 and rear end cap 46. A portion of front end cap 45 forms a handle 47 which serves also as a base for control valves and ducts.

The front end of compression tube 33 has screwed therein a buffer member 51 having a tubular extension member 52 projecting rearwardly therefrom and adapted to contact the gripping chuck 43 to hold it in non-gripping position.

Gripping chuck 43 includes an outer casing 53 which contains a spring 54 that urges three wedge-shaped jaw segments 55 forwardly and toward each other. When chuck 43 is moved rearwardly, jaw segments 55 grip the wire 24 and pull it along. When chuck 43 is moved forwardly, jaw segments 55 are moved rearwardly and away from each other by frictional contact with wire 24, against the action of spring 54, and exert no gripping action on wire 24.

When chuck 43 is moved to its extreme forward position, tubular extension member 52 moves jaw segments 55 rearwardly and away from each other against the action of spring 54 to assume a non-gripping position.

Anchor 23 is of similar construction to chuck 43, except that an end cap 56 is provided, and forms a seat for spring 57 (which urges three jaw segments 58 forwardly and toward each other to grip the wire 24).

So that wire 24 may extend all the way through jack if desired, rod 42 is provided with a bore 61, piston 41 with a bore 62, and extension rod 63 (mounted on piston 41 and extending rearwardly therefrom to project rearwardly from housing is provided with a bore 64. When extension rod 63 is not used, the wall of rear end cap 46 has no opening therein, and wire 24 is insertable into tensioning rod 42 only as far as piston 41. Such a structure is indicated in FIG. 10, for example.

It is to be noted that anchor 23 is a standard commercial item used for anchoring wires or rods in pie-stressed concrete panels. The inner bore of anchor 23 is tapered so that the three jaw segments 58 tighten against wire 24 under the urging of spring 57 whenever the wire 24 is pulled toward the smaller end of the tapered bore (i.e., in FIG. 2 when wire 24 moves forwardly toward the left, jaw segments 58 clamp down against wire 24).

The normal non-gripping condition of jack 25 is illus trated in FIG. 5 with chuck 43 in its most forward position and with tubular extension 52 of buffer member 51 pressing against and pushing jaw segments 55 against the action of spring 54 and away from the small end of the tapered bore of casing 53. This action frees the jaw segments 55 so that they may ride freely over wire 24. This non-gripping position of jack 25 is used when the wire 24 is being inserted into, or being removed from, the jack.

In operation, wires 24 are stretched between spaced apart abutment walls 22 over bed 21 and are held in position by anchors 23. Enough Wire is left protruding from anchors 23 to provide a gripping length for chuck 43. The end of wire 24 is fed through the open jaws of chuck 43 until buffer member 51 abuts end cap 56 of anchor 23.

Then chuck 43 is moved rearwardly by introducing a low pressure, for example 100 pounds, into front portion 65 of pressure chamber 3'7 to exert pressure against the front face of piston 41 and move it rearwardly. Jaw segments 55 move out of engagement with tubular extension member 52 and grip the wire 24.

With compression tube 38 acting against anchor 23, wire 24 is tensioned until the tension force equals the 100 pound force of the hydraulic pressure. This operation removes any slack from the wire 24 and places it in condition for the next step, the application of the desired tension.

Although it is possible to subject wire 24 to the step of applying the final tension without first taking out the slack in Wire 24, it is preferable to take out the slack since then the piston 41 is moved to its extreme forward position and the full length of the piston stroke utilized in applying the final tension to wire 24. Also releasing the tension on wire 24, after the slack has been taken out of it, permits the operator to ascertain whether or not the anchors 23 are holding the wire 24 properly without slippage.

FIG. 6 illustrates the operation of jack 25 as it takes up slack in wire 24. Low pressure, for example 100 pounds, enters a handle duct 66 and flows through a valve 67 (which has been pushed down), a duct 63, and a vertical duct 71 into front portion 65 of chamber 37. The fluid escapes from cylinder rear portion 72 through a duct 73, a valve 74, and a duct 75 which connects to exhaust line 29.

FIG. 7 illustrates the operation of jack 25 as piston 41 is moved forwardly to the non-gripping position of chuck 43 as illustrated in FIG. 5. Low pressuure (e.g., 100 pounds) enters through low pressure line 28 which connects to duct 66 and flows through a duct 75, valve 74 (which has been depressed), and duct '73 to rear portion 72 of chamber 37. The fluid from front portion 65 of cham er 3'7 is exhausted through duct 71, a duct 77, and duct 75 which connects to exhaust line 29.

FIG. 8 illustrates the operation of jack 25 when wire 24 is being subjected to its predetermined tension stress. High pressure, for example 1500 pounds, flows through high pressure line 27 into a duct 78, through a valve 79 (which has been depressed), duct 80, and duct 71 into front portion 65 of chamber 37. The fluid is exhausted from rear portion 72 of chamber 37 through duct 73, valve '74, and duct 75 to exhaust line 29. Valve 79 is kept open until piston 41 stops moving. There is no necessity for watching the distance that the piston moves since the pressure value has been predetermined so as ;to exert the required pull on wire 24. However, a slot 83 is provided in compression tube 38, and the progress of chuck 43 may be checked against a scale 84 which is marked along slot 83.

When the pressure value on the piston 41 equals the tension value of the wire 24, piston 41 stops moving, and wire 24 has been tensioned and stretched the required length. Since anchor 23 passes wire 24 freely when the wire is being pulled by jack 25, wire 24 must move forwardly in the direction away from the jack for a slight distance in order for anchor 23 to grip and hold.

The pressure on piston 41 and the length of piston travel is adjusted to compensate for this by moving the piston a slightly greater distance than the final stretch of the wire 24 to be obtained.

After wire 24 has been fully stretched, piston 41 is moved to its extreme forward position so that jaw segments 55 of chuck 43 are moved into non-gripping position by extension member 52 of buffer member 51. The jack may then be removed from wire 24.

To make the jack still lighter in weight, the valves may be removed from the handle and mounted on the hydraulic fluid pressure supply unit 85 (FIG. 9) by installing electric switches 86-88 on handle 91 and utilizing solenoid operated valves 92% (FIGS. 9-10). The jack 97 may be used for handling and stretching the wire only, except for supporting the three switches and their wiring and providing a duct 98 leading to the front portion 65 of chamber 37 and a duct 101 leading to the rear portion 72 of chamber 37. Duct 38 connects with line 102 and duct lill connects with line 103. Switches 86-88 are connected to a battery 104 or other source of electricity by electrical conductors 105.

Switch 86 operates solenoid operated valves 94, and 96 (which are equivalent to valve 74) to move piston 41 forwardly by admitting low pressure through conduit 1%, conduit 1&7, valve 95, line 103, and duct IM to rear portion 72 of chamber 37.

- ently preferred embodiment.

The fluid is exhausted from front portion 65 of chamber 37 through duct 98, line 102, conduit 108, valve 94, and conduit 111.

Switch 87 actuates solenoid operated valve 93 (which is equivalent to valve 67) to admit low pressure into front portion 65 of chamber 37 to take out the slack in the wire 24. Low'pressure passes from conduit 106 through valve 93, conduit 108, line 102, and duct 98 into front portion 65 of chamber37. Fluid is exhausted from rear portion 72 of chamber 37 through duct 191, line 103, valve 96, and conduit -111.

Switch 88 actuates valve 92 (which is equivalent to valve 79) to tension the wire 24. High pressure moves through conduit 112, valve 92, line 102, duct 8 into front portion 65 of chamber 37. Fluid exhausts from rear portion 72 of chamber 37 through duct 161, line 103, valve 96, and conduit 111.

It is to be understood that the form of the invention herewithshown and described is to be taken as a pres- 'arious changes may be made in the shape, size and arrangement of parts. For example, equivalent elements may be substituted for those illustrated and described herein, parts may be reversed, and certainfeatures of the invention may be utilized independently of the use of other features, all without departing from the spirit or scope of the invention as defined in the subjoined claims.

The claimed invention:

1. A hydraulic jack comprising a housing containing a hydraulic pressure chamber, a compression tube extending from said housing and having a front end adapted to abut an anchor used to hold a tension wire, a piston positioned in said chamber, a tensioning rod connected to said piston and extending from said chamber and positioned within said compression tube, gripping means located on the front end of said rod adapted to grip the wire when it is being subjected to tension stress, hydraulic pressure means connected to said chamber for moving said piston and tensioning rod and gripping means relativeto said chamber and compression tube, which are fixedly positioned, to pull the wire and exert a tension stress thereon, and means automatically urging the gripping means to gripping, position when the tensioning rod is being retracted to tension the wire and automatically releasing the gripping means when the tensioning rod is being extended.

2. The hydraulic jack defined in claim 1 wherein a buffer member is mounted in the front end of said compression tube, said gripping means including an outer casing containing therein a spring which urges wedgeshaped jaw segments forwardly and toward each other,

4; The hydraulic jackdefined in claim 3, wherein is also provided a handle mounted on said housing,-and a source of hydraulic pressure, and wherein said control means includes said low pressure fluid feed means which has a first means for applying hydraulic fluid under low pressure to the front portion of said chamber to move said piston in the direction away from the front end of said compression tube and thereby take the slack out of the wire, and has a handle duct leading to the front portion of said chamber with a valve positioned in said duct, and has second means for applying hydraulic fluid under low pressure to the rear portion of said chamber to release the wire and move said piston in the direction toward the front end of said compression tube, the second said means including a handle duct leading to the rear portion of said chamber with a valve positioned in said duct, and said high pressure fluid feed means has means for applying hydraulic fluid under high pressure to the front portion of said chamber to move said piston in the direction away from the front end of said compression tube and to exert a tension stress on the wire to stretch it to a predetermined length, and has a handle duct leading to the front portion of said chamber with avalve positioned in said duct.

5. Apparatus for tensioning a wire used to pre-stress concrete and the like, comprising anchor means adapted automatically to permit movement of the wire therethrough when the wire is stretched by being subjected to tension stress but which automatically holds the wire against retracting when the tension stress is removed, a compression tube adapted to abut against the anchor means, a housing connected to the compression tube and containing a hydraulic pressure chamber, a piston positioned in said chamber, a tensioning rod mounted on said piston and extending from said chamber and positioned within said compression tube, gripping means located on the front end of said rod adapted to grip the wire when it is being subjected to tension stress, hydraulic pressure means connected'to said chamber for moving said piston and tensioning rod and gripping means to pull the wire and exert a tension stress thereon and means automatically urging the gripping means to gripping position when the tensioning rod is being retracted to tension the wire and automatically releasing the gripping means when the tensioning rod is being extended.

6. A hydraulic jack for tensioning a wire used to prestress concrete comprising a housing including a jack and a fixed extension member projects rearwardly from said buffer member and is adapted to contact said jaw segments of said gripping means to hold them in nongripping position.

3. A hydraulic jack comprising a housing containing a hydraulic pressure chamber, a compression tube extending from said housing and having a front endadapted to abut an anchor used to hold a tension wire, a piston positioned in said chamber, a tensioning rod connected to 'said piston and extending from said chamber and positioned within said compression tube, gripping means located on the front end of said rod adapted to grip the wire when it is being subjected to tension stress,'hydraulic pressure means connected to said chamber for moving said piston and tensioning rod and gripping means to pull the wire and exert a tension stress thereon, and control said control means including alow pressure fluid feed' cylinder having front and rear end caps which form a hydraulic pressure chamber, a compression tube extending from the front end cap, a buffer member mounted in the front end of the compression tube and adapted to abut against an anchor used to hold the tension wire, a piston positioned in said chamber and having a hollow bore which may permit passage of the wire, a hollow tensioning rod mounted on said piston and extending from said chamber and positioned within said compression tube,

a gripping chuck mounted on the front end of said rod for controlling the operation of the jack, said control means and a high pressure fluid feed means, and valves for controlling the operation of said feed means,

:control means includes electrical switches mounted on said handle and connected to solenoid valves mounted elsewhere which control the application of high, low,

and exhaust pressure to the front and rear portions of said compression chamber.

References Cited in the file of this patent UNITED STATES PATENTS Jansen May 3, 1960 Sims May 2, 1961 Carlson et a1. Mar. 19, 1963 Paul May 21, 1963 FOREIGN PATENTS France July 2, 1956 Great Britain Dec. 19, 1951 Great Britain Apr. 17, 1957 Great Britain Aug. 21, 1957 

1. A HYDRAULIC JACK COMPRISING A HOUSING CONTAINING A HYDRAULIC PRESSURE CHAMBER, A COMPRESSION TUBE EXTENDING FROM SAID HOUSING AND HAVING A FRONT END ADAPTED TO ABUT AN ANCHOR USED TO HOLD A TENSION WIRE, A PISTON POSITIONED IN SAID CHAMBER, A TENSIONING ROD CONNECTED TO SAID PISTON AND EXTENDING FROM SAID CHAMBER AND POSITIONED WITHIN SAID COMPRESSION TUBE, GRIPPING MEANS LOCATED ON THE FRONT END OF SAID ROD ADAPTED TO GRIP THE WIRE WHEN IT IS BEING SUBJECTED TO TENSION STRESS, HYDRAULIC PRESSURE MEANS CONNECTED TO SAID CHAMBER FOR MOVING SAID PISTON AND TENSIONING ROD AND GRIPPING MEANS RELATIVE TO SAID CHAMBER AND COMPRESSION TUBE, WHICH ARE FIXEDLY POSITIONED, TO PULL THE WIRE AND EXERT A TENSION STRESS THEREON, AND MEANS AUTOMATICALLY URGING THE GRIPPING MEANS TO GRIPPING POSITION WHEN THE TENSIONING ROD IS BEING RETRACTED TO TENSION THE WIRE AND AUTOMATICALLY RELEASING THE GRIPPING MEANS WHEN THE TENSIONING ROD IS BEING EXTENDED. 